This invention pertains to a copper infiltrating paste for infiltrating a porous mass of ferruginous material and particularly to a residue-free high density infiltrating paste.
The strength of iron powder compacts can be increased by infiltrating the compacted powder iron matrix with a metal having a melting point lower than that of iron. The lower melting infiltrant is placed on the surface of the iron compact in the amount sufficient to fill the voids in the compacted iron matrix upon heating to a temperature sufficient to melt the infiltrant. The resulting mass is often heated to a temperature sufficient to sinter the iron as well as melting the infiltrant and such a process is known in the art as "sintration" or sintrating. The resulting infiltrated compact has a final strength greater than that of a non-infiltrated iron powder compact. Infiltrating processes for iron base compacts ordinarily provide copper infiltrating powder, iron or other metal to reduce erosion of the iron compact, and a refractory parting compound to facilitate removal of residue remaining after infiltration. The infiltrating composition is usually preformed into a slug which is then placed on the iron compact for filtrating.
Various infiltrating compositions suggested in the past, however, very often leave a residue which adheres to the infiltrated compact. The residue often sticks to the infiltrated part and must be chipped or ground off after the infiltration is completed. Erosion of the infiltrate compact is a further problem due to iron from the compacted iron matrix being dissolved by copper. Pre-alloyed copper with iron has been suggested, but these infiltrating materials leave a residue or otherwise causing sticking and roughness. Hardening compounds or refractories such as magnesium oxide or titanium oxide are incorporated into the infiltrating composition for the purpose of releasing a residue left behind from the infiltrating composition. For example, U.S. Pat. No. 3,307,924 suggests an infiltrate composition preformed into a slug that leaves a residue which shrinks and warps into a husk-like residue which may be easily removed from the infiltrated part; whereas, U.S. Pat. No. 3,619,170 suggests the inclusion of minor amounts of iron-chromium alloy within the infiltrating composition which substantially reduces the tendency of such residues to adhere and/or erode the infiltrated metal compact whereby the remaining residue can be removed by a gravitational force. Accordingly, prior art processes for infiltrating iron compacts provide refractory materials in the infiltrating paste for the purpose of facilitating removal of residues remaining from the spent infiltrating pastes after infiltration.
It now has been found that a residue-free, high density, copper infiltrating paste of flowable consistency can be applied to a compacted iron matrix and virtually elimintes the residue remaining after sintrating or infiltrating the compacted metal powder.
Accordingly, the primary object of this invention is to provide a high density, residue-free infiltrating paste comprising a powder metal blend of powder copper and minor amounts of powder iron suspended in a vehicle to form an infiltrating paste of flowable consistency that can be expediently applied to the iron compact from a dispenser.
A further object is to provide a residue-free infiltrating paste free of refractory parting compounds.
A further object is to provide an infiltrating paste for imparting good strength to iron powder compacts with negligible erosion to the iron compact.
A still further object is to flowable infiltrating paste that can be dispensed automatically from a dispenser and applied directly as received from the dispenser to an iron compact without the intermediate step of preparing infiltrating slugs.
A further object is to provide an infiltrating material for imparting good strength to iron powder compacts without eroding the base metal.
These and other advantages of this invention will become more apparent by referring to the Detailed Description of the Invention.